Photosynthesis

Photosynthesis is the process by which plants convert light energy into chemical energy in the form of sugars and other organic compounds. It involves a series of reactions requiring carbon dioxide and water and light. The process of photosynthesis takes place in the chloroplasts, specifically using chlorophyll, the green pigment involved in photosynthesis. Light energy drives these reactions. Oxygen is released as a byproduct of the process.

The following equation summarizes photosynthesis:

6 CO2 + 6 H2O——> 6 (CH2O) + 6 O2

In photosynthesis, electrons are transferred from H20 to CO2 molecules which form energy rich sugar molecules. Carbon dioxide is converted into sugars in a process called carbon fixation. This is an example of oxidation reduction process. Water is oxidized while CO2 is reduced. Light energy is used to drive electrons from water to more energetic states in sugars. Thus, solar energy is converted into chemical energy.

Photosynthesis is an important process because the existence of life on earth depends on it. It is the only process by which solar energy is trapped and converted by plants into food for the rest of the organisms. It is also the most massive and interesting chemical event on the earth. The average rate of energy capture by photosynthesis globally is immense, approximately 130 terawatts, which is about six times larger than the power consumption of human civilization

Magnitude and importance of photosynthesis

Photosynthesis is importance for a number of reasons. From our point of view, it is important because it produces food and oxygen without which life is not possible. Only the plants utilize solar energy by the process of photosynthesis. Animals derive food from plants and get energy by respiration. Photosynthesis also releases oxygen which is essential for the survival of animals and humans.

All the food we eat, the fuel we burn and the clothes we wear are directly or indirectly derived from plants. All of these are obtained from photosynthesis. Man uses plants for fodder, timber, fibers, etc. Fossil fuels such as coal and petroleum are also derived from plants which lived on earth millions of years ago.

Plants growing in the oceans account for 90% of the total photosynthesis. Photosynthesis produces 170 millions tones of dry organic matter every year. Out atmosphere contains 0.03 percent of carbon dioxide. This amount of CO2 is sufficient to sustain photosynthesis only for a few 100 years. Only 0.2 percent of solar energy that is incident on the earth is used for photosynthesis.